The Metropolitan Water District of Southern California is a regional wholesaler that provides water for 26 member public agencies to deliver - either directly or through their sub-agencies - to nearly 19 million people living in Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Ventura counties. The district imports water from the Colorado River and Northern California to supplement local supplies, and helps its members develop increased water conservation, recycling, storage, and other resource-management programs.

The mission of the Metropolitan Water District of Southern California is to provide its service area with adequate and reliable supplies of high-quality water to meet present and future needs in an environmentally and economically responsible way.